This article compares two historical massacres that resulted from ethnic antagonism during the Japanese colonial period: the massacre of Koreans and Chinese by the Japanese during the Great Kanto Earthquake in 1923 and a series of anti-Chinese riots and the massacre of Chinese that erupted in colonial Korea in 1931. A similar trajectory led up to both massacres: most of the assailants and victims were lower-class male workers, and both incidents occurred during economic depressions when competition between indigenous workers and immigrants had intensified due to a massive influx of migrant labor. The fact that the majority of the assailants were from the lower class suggests that their own resentment, long condensed from years of experiencing discrimination in their home society, combined with nationalism and anti-foreignism to explode in the form of massacres. In addition, the reality that all assailants were male workers implies that their value system, their mode of life, and the consciousness of a patriarchal hierarchy, which dominated the everyday lives of the male workers of the lower class, were transformed into violence under exceptional circumstances. Lastly, the fact that the victims of the two massacres were migrant workers means that, from the outset, the trigger for the massacres can be understood from a transnational perspective on migrant labor and cannot be confined to the boundary of a single nation. Keywords: Japanese empire, colonial Korea, massacres, riots, Great Kanto Earthquake, scaremongering, ethnic prejudice, migrant labor, masculinity, East Asian migration history